JPS60211752A - Ion beam generation device - Google Patents

Abstract

PURPOSE:To greatly improve the ionizing efficiency and the ion selectivity by a method, in which a material to be ionized is excited by gas discharge in a relatively low excitation state while being optically excited in resonance to the Rydberg state by the irradiation of a laser beam and further brought into an ionized state by collision of electrons due to gas discharge. CONSTITUTION:Beryllium vapor 10 is introduced into a container 1 from a gas introduction hole 1a. The voltage is impressed on the electrodes 5 and 6 synchronizing with laser oscillation. The electrons collide with beryllium vapor 10 due to gas discharge for exciting the beryllium vapor 10 into a quasi-stable state. The laser beams B4 and B6 are introduced through a window 3a, while the laser beam B5 is introduced through the window 3b for being resonantly excited stepwise into the Rydberg state and finally ionizing the excited vapor by the collision of electrons due to gas discharge. The direct current voltage is impressed between the electrodes 6 and the sample stand 8a, while the ion beam 9 is radiated on the sample 8.

Description

[Detailed description of the invention] [Technical field of invention] The present invention is applicable to material modification including semiconductor processing equipment.

This relates to ion beam generators used for materials synthesis, etc.

[Prior art]

Conventionally, various methods have been considered and put into practical use as ion generation methods using ion beam generators. Most of them used electric discharge, but in recent years ion sources using laser light have been devised. There are two methods that use light such as laser light. One is to irradiate a solid such as a metal with laser light and use the resulting plasma as an ion source, or to focus the laser light and convert it into gas or liquid. irradiation to create plasma, which is used as an ion source.
The other method uses a variable wavelength light source to ionize a substance by resonating a single wavelength such as a laser beam with the energy level of the substance to be ionized. It is related to.

[Summary of the invention]

The present invention provides an ion beam generator using resonant light excitation and ionization as described above, in which the substance to be ionized is set in the Rydberg state (R
The purpose of this project is to provide an ion beam generator that can improve the ionization efficiency for input light energy by several orders of magnitude compared to conventional resonant optical excitation and ionization methods, and has excellent selectivity in selective ionization. There is.

[Embodiments of the invention]

First, the ionization method in the apparatus of the present invention will be explained by comparing it with a conventional method using an example in which a beryllium ion beam is generated. FIG. 1 is an energy level diagram of beryllium neutral atoms.

In the conventional ionization method, for example, the wavelength is 2349.

Three laser beams B1 for 4573 people and 5000 people.
This is a method of irradiating beryllium vapor to be ionized with B2 and B3. In other words, the helium atoms in the ground state 2s (13) are first resonantly excited to the first excited state 2p ('PO) by the 2349 laser beam Bl. then 457
Energy level 3d (ID
), and further 5000 laser beam B3
It ionizes it.

- The ionization method in the device of the present invention differs from the conventional ionization method described above in that the beryllium vapor is brought into a state in which the metastable state 2p (3PO) is predominant by gas discharge, and the laser beam, in the example of FIG. Wavelength 3321 people, 1
．． 46μ, 3 laser beams B4-B of 6449 people
6, the excited vapor is changed from the excited state to the Rydberg state, and furthermore, as in the conventional ionization method, the beryllium vapor is irradiated with a laser beam, B3 in the example of FIG.
The point is that the excited state is changed from the excited state to the ionic state by gas discharge, rather than being brought into a free electronic state, that is, an ionic state.

In the case of the ionization method in this inventive device, the collision cross section for ionization is several orders of magnitude higher than in the conventional ionization method, in which beryllium vapor is directly ionized from the energy level 3d (ID) using a laser beam B3 with a wavelength of 5000. . Therefore, the output energy of the laser beam is small, and since the excitation is from a metastable state rather than the ground state, the wavelength of the photon is short, and since only resonance is used, the energy level of the laser beam By selecting wavelengths that do not match those of impurity atoms, it is possible to ionize only the substance to be ionized, and moreover, it is possible to ionize the substance with high purity.

Furthermore, by changing the wavelength of the laser beam, ion beams of other types of substances can be easily generated, and in this case, various types of substances to be ionized may be introduced into the ion beam generation container in advance. . The method of the present invention, which allows the type of ion beam generated to be easily changed, is different from conventional methods, and has the advantage of being able to perform two or more processing steps using an ion beam in succession. be.

Next, embodiments of the invention will be described with reference to the drawings.

FIG. 2 shows a first embodiment of the invention. In the figure, 1
1a is a container into which the substance to be ionized is introduced; 1a is a gas introduction hole for introducing the substance into the container 1; 1b is a gas introduction hole for introducing the substance into the container 1;
3a or 3b is a gas exhaust hole, and 3a or 3b is a laser beam B4. This is a window through which B6 or B5 is introduced into the container 1, and the space in the container 1 where the laser beams 84 to B6 intersect is the ion generation space 4. Note that as the laser beam generating section, a laser such as a wavelength tunable laser or a free electron laser is used.

Reference numerals 5.6 and 5.6 are electrodes arranged across the ion generation space 4; 5a and 5a are terminals for applying voltage to the electrodes 5.6; It constitutes the generating section 15. , 8 is a sample, 8a is a sample stand that holds the sample 8, and the sample stand 8
A DC voltage is applied between a and the electrode 6, thereby generating an extraction electric field for extracting the ionized substance as an ion beam.

Next, the operation will be explained.

Let us consider the case where a beryllium ion beam is generated by the apparatus of this embodiment. First, beryllium vapor 10 is introduced into the container 1 through the gas introduction hole 1a. Then, the laser beam generating section oscillates, and a voltage is applied to each of the electrodes 5 and 6 from the terminals 5a and 6a in temporal synchronization with the laser oscillation. Then, due to this, the above ground state 2s('S)
Electrons from the gas discharge collide with the beryllium vapor 10 located at
3PO). Furthermore, laser beams B4 and B6 of 3,321 and 6,449 people were introduced into the container 1 through the window 3a, and a laser beam B6 of 1,46μ was similarly introduced through the window 3b. , each of the beams B4 to B6 intersect in the ion production space 4 in the vessel 1, so that the beryllium vapor 10 is 332
The metastable state 2p (3PO
) to the excited state 3s (33), and further 1
．． The above excited state 3g (
33) to the excited state 3p (3PO), and is further resonantly excited stepwise to the Rydberg state 12d (3D) by the 6449 laser beam B6, and finally the excited vapor is excited by the collision of electrons due to the gas discharge. Ionized. Further, a DC voltage is applied between the electrode 6 and the sample stage 8a, whereby the ionized beryllium vapor 1o is extracted as an ion beam 9 consisting only of beryllium ions. The sample 8 is irradiated.

The characteristics of this embodiment in the above operation description are as follows: First of all, since this embodiment performs selective ionization completely using only resonance, the substance to be ionized in the volume B1, in this case, Even if it contains impurities other than beryllium, such as oxygen, nitrogen, carbon, hydrogen, etc., and the amount thereof is greater than beryllium, the energy level and wavelength of the laser beam should not match those of the above impurities, etc. The result is a pure beryllium ion beam in which only the desired element, in this case beryllium, is ionized.

Second, as mentioned above, this embodiment performs selective ionization and ionization by resonant optical excitation, so there is no possibility that electrons or other elements will be excited or that the temperature will rise due to energy absorption. As a result, low-temperature processing can be performed without increasing the temperature of the target sample 8 to be irradiated with the ion beam, such as a substrate in the case of a semiconductor.

Third, if you want to change the type or characteristics of the ion beam, you can simply change the wavelength of the laser beam, and there is no need to take out the sample or open and close the container to replace the ion source, as in the past. , continuous operations such as ion implantation and annealing can be easily performed.

FIG. 3 shows a second embodiment of the invention. In the figure, the same reference numerals as in FIG. 2 indicate the same or equivalent parts, 13 is an oven containing the substance 12 to be ionized, 13a is a heater provided on the outer periphery of the oven 13, and 11 is ionized beryllium vapor. 10 is a magnet that focuses the ion beam on the axis of the container 1, and 14 is an extraction electrode that extracts the focused beryllium vapor 10 as an ion beam 9.

Next, the operation will be explained.

When beryllium 12, which is a substance to be ionized, is placed in the oven 13 and the oven 13 is heated by the heater 13a, the beryllium 12 is melted.

The beryllium vapor 1O is vaporized and is introduced into the container 1 through the gas introduction hole 1a. Then, a voltage is applied to the electrodes 5 and 6, and electrons due to gas discharge collide with the vapor 10, and at the same time, 3321 people and 6449 people
Human laser beam B4. B6 passes through the window 3a, and 1
, 46μ laser beam B5 is introduced into the vessel l through the window 3b and irradiates the vapor lO, thereby causing the vapor 10 to change from the ground state 2s ('S) to the excited state 2p (3P').

The electrons of the beryllium vapor 10 in the Rydberg state 12d (3D) are excited in a stepwise manner through 3s (3S) and 3p (3PO), and the electrons in the beryllium vapor 10 in the Rydberg state 12d (3D) become free electrons, thereby creating an ion generation space. Beryllium ions are generated at 4, and after being focused to the axis by the magnet 7) 11, they are emitted as an ion beam 9 by the extraction electrode 14.

FIG. 4 shows an example of the configuration of a laser oscillation device in an ion beam generator according to a third embodiment of the present invention.

In the present invention, the laser beam and gas discharge for ion generation need to be synchronized in time, and in order to excite the elements in a stepwise manner, a plurality of laser beams each having a specific frequency are required. Of course, it is necessary to synchronize a plurality of laser beams, and FIG. 4 shows an example of a synchronization method.

This laser oscillation device 20 includes three wavelength-tunable dye lasers 22, 23, 24, an excitation source laser 21 for exciting each of the dye lasers 22 to 24, and half mirrors 25, 2.
6 and a total reflection mirror 27. By configuring the excitation source with one b laser 1 in this way, the oscillated laser beams ωl, ω2 . ω3 becomes temporally synchronized. and oscillation of the excitation source laser 21,
By applying voltage to the electrodes 5.6 at the same time, the laser beam and the gas discharge can be synchronized in time.

〔Effect of the invention〕

As described above, according to the ion beam generator according to the present invention, the substance to be ionized is excited to a relatively lower excited state by gas discharge, and the substance to be ionized is changed from the excited state to the Rydberg state by irradiation with a laser beam. Resonant optical excitation to
Furthermore, since the substance is changed from the excited state to the ion state by collision with electrons from the gas discharge, the ionization efficiency and ion selectivity can be greatly improved.

[Brief explanation of drawings]

FIG. 1 is an energy phase diagram of a singlet system of beryllium neutral atoms, FIG. 2 is a schematic configuration diagram of a shower type ion beam generator according to the first embodiment of the present invention, and FIG. A schematic configuration diagram of a focused ion beam generator according to an embodiment, and FIG. 4 is a block diagram of a laser beam oscillator of an ion beam generator according to a third embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Container, 15... Gas discharge generating part, 20...
Laser beam generating section, Bl to B6...Laser beam. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent: Masuo Oiwa Figure 4 procedural amendment (voluntary) 2. Name of the invention Ion beam generator 3. Person making the amendment Relationship to the case Patent applicant address 2 Marunoshiratama-chome, Chiyo 113-ku, Tokyo 3rd name
Name (601) Mitsubishi Electric Corporation Representative Hitoshi Katayama 4, Agent address 2-1 Marunouchi 2-chome, Chiyome-ku, Tokyo 2-3 So5,
? 1. Detailed description of the invention in the original subject specification and drawings (Figure 1) 6. Contents of the amendment +11 ``The substance...'' in lines 1-2 on page 5 of the specification
...(Rydberg 1evel) Correct J to Rydberg state (Rydberg 5tate) j. (2) Correct Figure 1 as shown in the attached sheet.

Claims (1)

[Scope of Claims] (11) A container containing a substance to be ionized, a laser beam generator that irradiates the substance in the container with a laser beam, and a laser beam that intersects with the substance in the atmosphere of the substance in the container. A device for generating an ion beam of the above substance, comprising: a gas discharge generating unit that generates a gas discharge;
The gas discharge generating unit excites the substance from a ground state of energy level to a relatively lower excited state by gas discharge,
The substance is obtained by irradiation with a laser beam, which will be described later, or changed from the Rudberg state to an ion state, and the laser beam generating section resonantly excites the substance from the relatively lower excited state to the Rydberg state. An ion beam generator characterized in that it generates a laser beam having a wavelength. (2) The laser beam generating section generates a plurality of laser beams with different wavelengths that resonate and excite the substance stepwise from the relatively lower excited state to the Rydberg state via the intermediate state. An ion beam generator according to claim 1, wherein the ion beam generator is an ion beam generator. (3) The ion beam generator according to claim 1 or 2, wherein the relatively lower excited state is a metastable state. (4) The ion beam generator according to any one of claims 1 to 3, wherein a wavelength tunable laser is used as the laser beam generator. (5) The ion beam generator according to any one of claims 1 to 3, wherein a free electron laser is used as the laser beam generator. (6) The above-mentioned laser beam generating section is composed of one excitation source laser and a plurality of mutually time-synchronized dye lasers excited by the laser beam from the excitation source laser. The ion beam generator according to item 2 or 3. (7) The ion beam generator according to any one of claims 1 to 6, wherein the gas discharge generating section generates a high-frequency discharge. (8) The substance is introduced into the container as a compound or molecular gas, and the gas discharge also serves as a gas discharge to bring the substance introduced into the container into a neutral element state. An ion beam generator according to any one of claims 1 to 7, characterized in that: (9) The ion beam generator according to claim 7, wherein the gas discharge generating section has a high frequency power source that resonates so that the substance changes from its Rydberg state to an ionized state. .